Sun Crosses Celestial Equator
The September equinox occurs the moment the Sun crosses the celestial equator – the imaginary line in the sky above the Earth’s Equator – from north to south. This happens either on September 22, 23, or 24 every year.
The Axial Tilt
The Earth’s axis is always tilted at an angle of about 23.5° in relation to the ecliptic, the imaginary plane created by the Earth’s path around the Sun. On any other day of the year, either the southern hemisphere or the Northern Hemisphere tilts a little towards the Sun. But on the two equinoxes, the tilt of the Earth’s axis is perpendicular to the Sun’s rays, like the illustration shows.
On the equinox, night and day are nearly exactly the same length – 12 hours – all over the world. This is the reason it’s called an “equinox”, derived from Latin, meaning “equal night”. However, even if this is widely accepted, it isn’t entirely true. In reality equinoxes don’t have exactly 12 hours of daylight
Customs around the September equinox
The September equinox coincides with many cultural events, observances and customs. It’s also called the “autumnal (fall) equinox” in the northern hemisphere and the “spring equinox” in the Southern Hemisphere.
September Equinox Customs
In many cultures, the September equinox is a sign of fall (autumn) in the northern hemisphere. In Greek mythology fall is associated with when the goddess Persephone returns to the underworld to be with her husband Hades. It was supposedly a good time to enact rituals for protection and security as well as reflect on successes or failures from the previous months.
Aboriginal Australians have, for a long time, had a good knowledge of astronomy and the seasons. Events like the September equinox, which is during the spring in Australia, played a major role in oral traditions in Indigenous Australian culture.
The Mid-Autumn Festival, also known as the Moon Festival, is celebrated around the time of the September equinox. It celebrates the abundance of the summer’s harvest and one of the main foods is the mooncake filled with lotus, sesame seeds, a duck egg or dried fruit.
Higan, or Higan-e, is a week of Buddhist services observed in Japan during both the September and March equinoxes. Both equinoxes have been national holidays since the Meiji period (1868-1912). Higan means the “other shore” and refers to the spirits of the dead reaching Nirvana. It is a time to remember the dead by visiting, cleaning and decorating their graves.
Pagan celebration: Mabon
On the autumnal equinox, many pagans celebrate Mabon as one of the eight Sabbats (a celebration based on the cycles of the sun). Mabon celebrates the second harvest and the start of winter preparations. It is the time to respect the impending dark while giving thanks to the sunlight.
The Christian church replaced many early Pagan equinox celebrations with Christianized observances. For example, Michaelmas (also known as the Feast of Michael and All Angels), on September 29, fell near the September equinox.